ph going UP??!!

[lauravanb]

I've been holding my Swiss style cheese at 122 for 50 minutes now. The pH is supposed to be 5.3-5.4 before draining. I used thermophilic c201 and propionic. Both packages were sealed before use and in the freezer. Ph readings are as follows:
12:25 - 6.24
12:38 - 6.34
12:49 - 6.33
12:53 - 6.23
12:59 - 6.39
1:03 - 6.42
1:15 - 6.45

I don't know if my cultures are dead somehow (I never overheated them), but even if so, how could it be getting more alkaline? That doesn't make any sense whatsoever! And is there anything I can do to fix this? At some point i might just say screw it and drain it.

[Kern]

When a meter goes contrary to what one expects, suspect the meter.  Milk fat can clog an electrode giving false readings.  In my experience these are usually higher than actual.  So, here is what I'd do in your situation:

1.  Wash the meter tip with dish detergent and warm water and rinse thoroughly.
2.  Check the meter against the pH buffer solution.  If it gives a correct reading then the electrode was most likely clogged.
3.  Recalibrate with the buffer solution.
4.  Check the cheese milk pH.  It sometimes takes a minute to get a good stable reading and you have to swish the tip around in the milk.
5.  Wash again as in #1 and store with meter tip in clear water.

If this doesn't solve the problem then ditch the meter and finish the cheese as per the recipe.

Incidentally, curds are usually drained at a pH of around 6.2-6.4 NOT 5.3-5.4.  Swiss style cheeses should come out of the press and be salted at 5.3 to 5.4.

[awakephd]

I have nothing to add to Kern's excellent advice, but I do have a question about your make. Are you sure you want the pH to get all the way down to 5.3 before draining? In general, this is the point at which I stop pressing (and move to the brine). Maybe you meant 6.3-6.4 ... but you have already reached that according to your readings.

Well, rats -- after looking more carefully, I see that Kern already addressed this issue as well. Sorry about the duplicate information ...

[lauravanb]

Incidentally, curds are usually drained at a pH of around 6.2-6.4 NOT 5.3-5.4.  Swiss style cheeses should come out of the press and be salted at 5.3 to 5.4.

I have nothing to add to Kern's excellent advice, but I do have a question about your make. Are you sure you want the pH to get all the way down to 5.3 before draining? In general, this is the point at which I stop pressing (and move to the brine). Maybe you meant 6.3-6.4 ... but you have already reached that according to your readings.

So... yeah... You guys were right. I was reading the directions on pressing, which is where it says to press to 5.3-5.4. I got it mixed up with the section above on cooking the curd. Whoops! So In that case, what do you think keeping the curd at 122 for so much longer than necessary will do to the final product? Make it drier? It knit very well on the press with an PSIs of .27 (15 min), .54 (30 min), 1.8 (x1 hr) and 1.8 x 14 hrs. I'm hoping that's a good sign.

I'm wondering why my first pH reading was already lower than target. I took it right when I reached 122. I guess I acidified too quickly, but I did go from 91 to 122 within the target amount of time. Is it undesirable to reach the target pH so quickly, or do you think it should have been held at 122 for some time while stirring before becoming that acidic?? There was no recommended amount of time in the recipe. Just a pH target (Caldwell's recipe).

Thanks guys!

[Kern]

Perhaps this will help.  I take the following pH readings and don't fret about possible others. 

Initial milk pH just before adding the culture.
pH after ripening, before renneting.  I'm looking for about a 0.05pH drop.  If it is 0.10 I don't worry about it.
Whey pH after cutting and cooking and/or stirring before drainage.  I'm looking for something in the 6.3 +/- range.  The curd and whey pH are close at this stage. 
Curd pH after initial draining.  Squeeze a small ball of curd to expel whey.  Curd is going to be in the low 6 range.  This is the top of the steep pH plunge so is a critical measurement.
Curd pH after first flip.
Curd pH after each subsequent flip to goal pH.

The curd pH drops rapidly from about 6.1 to 5.1.  Last weekend I made a Belper Knolle and saw the curd pH drop from 5.89 to 5.50 in one hour at 80F.  This is why these later readings are so important.  They will help you anticipate when the cheese should be put into the brine.  I don't put a lot of importance in the pressing schedule in a recipe.  I go by pH and if I have to press and flip on a faster schedule to get the final draining and rind closed by the time of the pH goal, then so be it.

[lauravanb]

The curd pH drops rapidly from about 6.1 to 5.1.  Last weekend I made a Belper Knolle and saw the curd pH drop from 5.89 to 5.50 in one hour at 80F.  This is why these later readings are so important.  They will help you anticipate when the cheese should be put into the brine.

Thank you for the info! Perhaps you can clarify something for me, as I'm new to the pH game. How are you getting curd ph exactly? Are you pinching off pieces of your curd during pressing at several points and then checking the pH? How often do you try this and doesn't it mar the wheel, especially if done toward the end of pressing? Do you discard the sample or replace it? And my pH meter is not a needle style, the probe is a ball that is protected by four plastic prongs. I'm not sure how I could check the pH of anything solid with that, except maybe by packing the curd around the ball??

Thanks again!

[Kern]

When the cheese is in the "curd state" I'll take a small wad of curd, squeeze out any whey and wad it up around the flat end of my Extech pH meter.  Usually, I'll wiggle it around a bit as the meter is stabilizing.  Although it is not good manufacturing practice I usually shred the curd wad and toss it back with the rest of the curds.  (You could not do this in a commercial operation and would have to toss it.)  But it is my cheese and I wear gloves and have sterilized the end of the pH meter with a weak bleach solution and rinsed it well.

In the pressing I depress the cheese with the pH probe before I flip it.  The depression will heal when the cheese is flipped but may leave a small mark.  Since I have taken several readings on the wheel while pressing I have a great feel for the pH drop versus time and estimate when the goal pH will be reached.  I don't bother with the final reading which would leave a dent in the cheese.

Your pH meter is vital to making reproducible cheeses that age into what you are striving for.  I suggest that you "over measure" on your first several cheese makes until you get a feel for what happens to the pH over time.  You will find that the steep drop occurs from about 6.1 to 5.1 or so but the time it takes to get there depends upon the amount, type of starter used and the ripening temperature.  Ideally, you want the cheese to be fully pressed before the goal pH is reached.   It is interesting to also measure the pH of the drained whey at the same time as you measure the cheese itself.  You'll see how fast the two measurements differ.

Finally, it is important to have your saturated brine solution cool and ready to go so that you can brine the cheese as close to goal pH as possible.